The present invention relates mainly to a brake booster that is adjustable, notably in terms of the value of the jump.
It is known practice to produce brake boosters that apply a force to a push rod of a master cylinder which force is an increasing function of the force applied by the driver to a control rod via a brake pedal. Typically, for a range of use, the boost ratio which is the ratio between the input force applied to the control rod and the output force from the booster and applied to the push rod, is constant. It is commonplace for several ranges of use to be employed, with several boost ratios, a first boost ratio for comfortable braking and a second boost ratio, higher than said first boost ratio, for emergency braking.
Among brake boosters of the known type, mention may, nonlimitingly, be made of vacuum pneumatic brake boosters, pressurized pneumatic brake boosters, hydraulic brake boosters (also known as hydroboost brake servos) as described, for example, in FR 2 727 370 and 49 49 61 846, pneumatic brake boosters with decoupling between the control rod and the push rod, like the one described, for example, in patent applications WO 2007/080106 and WO 2007/080158, and electric brake boosters like the one described in French patent application published under the number FR-2 860 474. Also known are brake boosters which further comprise means of commanding braking that are independent of the force applied by the driver to the brake pedal and widely known even in other languages by their English name of “active boosters”. One example of such a pneumatic booster is described in patent EP 0 478 396.
Brake boosters are also described in documents DE 10 2006 030168, WO 03/066405 and EP 0 716 969.
In the known way, the boost ratio is regulated by a reaction device, notably a reaction disk made of non-compressible elastomer or a small-diameter piston on which the pressure of a rear chamber of the master cylinder is applied.